1. Field of the Invention
This invention relates to an adhesive composition and a process for producing the adhesive composition, and more particularly, to an emulsion adhesive composition or a light resistant, emulsion adhesive composition suitable for adhering molded articles formed from highly crystalline resin such as polyolefin, nylon and the like to an optional material and a process for the production thereof.
2. Description of Related Art
Materials for motorcar parts and domestic electrical appliances have been recently made of plastics because of economy and light weight to a great extent. In particular, highly crystalline resins, for example, polyolefins such as polypropylene, polyethylene and the like and nylons are preferably used as the plastics.
However, since polyolefins and nylons are highly crystalline, when they are used in the form of a molded article, it is necessary to impart to them an adhesion property, before adhering, by treating the surface of the article with plasma or by applying a primer to the surface.
Indeed such treatments can render highly crystalline resin molded articles adhesive, but a complicated surface treating procedure is required and therefore, such treatments are very disadvantageous from the standpoint of commercial production.
The present inventors have intensively investigated adhesives capable of adhering molded articles of highly crystalline resins such as polyolefins and nylons with each other or with other materials such as optional materials without complicated surface treatments. As a result, the present inventors have found that the adhesive strength between highly crystalline resin molded articles such as polyolefins and nylons and an optional material when they are adhered, can be enhanced remarkably by using an adhesive composition produced by adding and mixing, under particular conditions, a conventional aqueous emulsion adhesive with a functional group-containing polyolefin and/or a block copolymer hydrogenated product composed of at least one aromatic vinyl compound polymer block and at least one aliphatic diene polymer block. Thus, the present invention has been completed.
Further, in connection with the above mentioned problems, some of the present inventors have already proposed in Japanese Patent Application Nos. 312592/1987 and 313634/1987 (hereinafter referred to as "inventions of prior applications") that a specified chlorinated polyolefin is added to a conventional aqueous emulsion adhesive and the resulting adhesive can markedly improve the adhesive strength when a molded article of a highly crystalline resin such as polyolefins and nylons is adhered to an optional material.
By using such adhesives proposed by the inventions of prior applications, molded articles of highly crystalline resins can be adhered to an optional material, but the light resistance to the sun light is poor depending upon the type of the materials to be adhered and circumstances where the molded articles thus adhered are used.
The present inventors have intensively researched so as to prepare an adhesive capable of solving the above mentioned problem. As a result, the present inventors have found that the light resistance can be enhanced by adding a photostabilizer to the adhesive of inventions of prior applications and the light resistance can be further enhanced and the storing stability can be improved by using a polyolefin containing chlorine and grafted with a monomer capable of radical polymerization in place of the chlorinated polyolefin, and further the introduction of specified functional groups in place of chlorine still gives the adhesion characteristics similar to those of the chlorinated polyolefin. Thus another aspect of the present invention has been completed.